Thermally responsive switch



Jan 16, 1962 c. GRlMsHAw 3,017,478

THERMALLY RESPONSIVE SWITCH Alfter/7 Jan. 16, 1962 c. GRlMsHAW THERMALLYRESPONSIVE SWITCH 2 Sheets-Sheet 2 Filed June 3. 1960 Unite StatesPatent 3,017,47 8 THERMALLY RESPONSIVE SWITCH Charles Grimshaw, Fulton,Ill., assigner to General Electric Company, a corporation of New YorkFiled .lune 3, 1960, Ser. No. 33,760 10 Claims. (Cl. Zilli-138) Myinvention relates to thermally responsive switches, and moreparticularly to such switches having two pairs of switch contactsactuated upon temperature change in opposite directions, with overtravelin temperature per mitted in both directions. Switches of this type areparticularly suitable for use as llame detectors in fluid fuel burningsystems, and the like.

To provide the desired overtravel in temperature, in flame detectingswitches of the prior art which have hot contacts and cold contactsselectively engaged by a movable contact, various types of frictionclutch arrangements have been utilized. These clutch arrangements areimportant to the function of such a switch, since they permit the switchto operate on temperature change rather than absolute temperature. Inllame detecting switches such as these, the friction clutch often slipswhen the switch environment cools down below normal room temperature, orwhen the switch has been severely Vjarred. Examples of this are wherethe llame detector switches are stored in a cold warehouse, or wherethey are severely jarred or shaken during shipment. After the switch hasbeen subjected to such colder temperatures or severe vibrations, whenthe switch is then brought into a warm room, the thermally responsiveelement warms up and the movable contact leaves the cold Contact, in thesame manner as it does when the thermally responsive element feels theheat of combustion. The master control or main control is so arrangedthat it will not start the burner unless the llame detector switch ismaking contact on its cold side. In order to properly start the burner,it has thus then been necessary for the person who is installing thellame detector switch or starting the burner to connect a temporaryjumper wire in the master control to short out certain terminals thereofso that the switch contacts will be in the proper starting position, oron the cold side. In order to eliminate the need of shorting out theterminals of the mastercontrol before starting the furnace, it has beenfound desirable to provide a means for maintaining the movable bimetalcontact in engagement with the cold contact under normal ambientconditions so that the switch contacts of the detector switch willalways be in the proper starting position even though the switch hasbeen shaken in shipment or subjected to very low ambient temperatures.It has also been found desirable to incorporate this selfstartingfeature in an improved ame detecting switch which is simple inconstruction and relatively inexpensive to manufacture.

Accordingly, it is the general object of my invention to provide a newand improved thermally responsive switch.

Another object of my invention is to provide an improved flame detectingswitch of the type having hot and cold contacts, where the cold contactswill be normally maintained in a closed position.

A further object of my invention is to provide an improved flamedetecting switch which is simple in construction and relativelyinexpensive to manufacture.

In carrying out my invention, in one form thereof, I apply it to athermally responsive switch which is used in a burner control circuit todetect the presence of flame, via radiation, and/or temperature change.This switch essentially includes a bimetallic arm with a movable contactmounted on its free end, a frictional clutch arrange- Patented Jan. 16,1962 ment for rotatably supporting the other end of the arm, and a pairof fixed contacts which selectively cooperate with the movable contactin response toflexure of the bimetallic arm. The two fixed contacts arethe cold and hot side contacts for the control circuit. To assure thatthe switch will normally maintain its movable contact in engagement withthe cold contact for properly starting the burner, a biasing rod isconnected to the supported end of the bimetallic arm. This rod serves asa rigid support for the bimetallic arm at all ambient temperatures belowa certain predetermined temperature. When the ambient temperature isabove this predetermined value, the biasing rod no longer has anysignificant operational effect upon the bimetallic contact arm. By usingsuch a biasing rod in my llame detecting switch, an expeditious andinexpensive means for normally maintaining the switch contacts on thecold side for starting the burner has thus been obtained.

By further aspects of my invention, additional desirable features may beincluded in the switch, and the specification concludes with claimsparticularly pointing out and distinctly claiming the subject matterthat I regard as my invention. The invention, however, as toorganization and method of operation, together with further objects andadvantages thereof, may best be understood with reference to thefollowing description when taken in conjunction with the accompanyingdrawings, in which: j

FIG. 1 is a plan view of an improved thermally responsive switchembodying my invention, in one form thereof, partially broken away toshow the internal parts of the switch more clearly;

FIG. 2 is a cross-sectional view taken substantially along the line A-Aof FIG. l;

FIG. 3 is a cross-sectional view taken substantially along the line B-Bof FIG. 2;

FIG. 4 is an exploded view showing the various parts of the switch ofFIG. 1, with the insulating base partially broken away and thetransparent cover removed;

FIG. 5 is a rear perspective view of the switch of FIG. 1, showing theterminals and a mounting bracket assembly, with leads affixed to theterminals; and

FIG. 6 is a view similar to FIG. l, with the transparent cover attachedto the base.

Referring now in detail to the drawings, and in particular to FIGS. land 2, there is shown a thermally responsive ame detecting switch 1wherein my invention has been advantageously employed. The switchhousing 3 includes hollow insulating base 5 and glass window or cover 7.Window 7 is fastened to the open side of base 5 and also sealed theretoby some suitable sealant material such as silicone rubber to provide atransparent cover for the switch 1. To make the manufacturing operationsimple, base 5 of my switch is of rectangular configuration, and it ismanufactured from some suitable insulating material such as the ceramicsteatite. Within hollow portion 9 of the base are sealed the operatingcomponents of my flame detecting switch 1.

To keep the cost of my switch 1 to a minimum, and also to provide aswitch which is very small in over-all size, as shown in FIGS. 2 and 4,the operating components of my switch 1 are very simple in construction.More particularly, in bottom wall 11 of base 5 (as shown in FIG. 4), Ihave formed slots 13, 15, and 17. Slot 13 is for receiving bearingterminal 21, and it extends through bottom wall 11 near end wall 19,being generally parallel to wall 19 and midway between the side walls.Terminal 21, as seen in FIGS. 2, 4, and 5, includes tab 23 which extendsoutwardly through slot 13 for electrical connection to a lead wire.Rectangularly shaped boss 25 is extended inwardly from bottom wall 11 ofbase 5. Side 25a of boss 25 is generally coplanar to the side of slot 13farthest away from end wall 19 and it serves to furnish additionalsupport for terminal 21 within cavity 9 by engaging intermediate portion29 of the terminal (see FIG. 4). Intermediate portion 29 of terminal 21has a pair of shoulders 27 which are coplanar with tab 23 for supportingthe terminal within the base. After tab 23 of the terminal 21 has beenextended through slot 13 and fastened in position on the outside (asshown in FIG. by some suitable sealant such as the aforementionedsilicone rubber, shoulders 2.7 are each held in secure engagement withthe inner surface of bottom wall 11.

For rotatably supporting thermally responsive arm 31 within base 5,bearing terminal 21 is bent over transversely along line 33, as shown inFIG. 4, and it includes a pair of curved bearing fingers 35 at its innerend. By bending terminal 21 along line 33, the engagement of theassociated upper edge 251? of boss 25 (as viewed in FIG. 4) with theline of bending of the terminal provides additional securement forbearing terminal 21 within base 5. The manner of rotatably mounting mythermally responsive arm 31 within base 5 of the liame detecting switchshall be described in detail hereinafter.

For an element which expands and contracts in response to thermal changeand thus detects the presence of an oil burner :llame via radiationand/or temperature change, in my switch 1 I have chosen the particularconstruction of bimetallic arm 31 (as seen in FIG. 4). Moreparticularly, arm 31 is made from a at strip of suitable thin bimetallicmaterial which is bent angularly intermediate its ends along line 30 sothat the high expansion side 31a has an intermediate angle in the orderof 163. In order to provide clearance for terminal 62 and also toincrease the bimetal energy output per weight of bimetallic materialused, the side edges 37 of bimetal 31 are convergent toward its free end39 so that the transverse width of the bimetal at its free end is lessthan the overall widths near and at its supported or pivoting end 41.Bimetal arm 31 has an appropriate aperture formed in its free end 39 forreceiving a riveted silver contact 43. Contact 43 extends outwardly fromboth sides of the biymetal to provide single pole double throw action inthe well-known manner.

To rotatably support arm 31 within base 5, supported end 41 of the armis stepped inwardly from side edges 37 and fastened to a smoothrotatable cylindrical member or pin 45 (see FIG. 4). To be morespecific, bimetal end 41 is welded tangentially to pin 45 and spacedequidistant from the ends of the pin. Portions of the smooth pin 45adjacent its ends then extend outwardly in a transverse manner fromunderneath the stepped sides of the bimetal to t into or underneath thecurved bearing fingers 35 of the terminal 21 (sce FIGS. 1 and 4).

To continuously bias bearing pin 45 into engagement with the curvedfingers 35 and thus furnish the desired clutching action for my flamedetecting switch 1, I have provided a U-shaped clutch spring 51 (seeFIG. 4). Spring 51 includes a generally flat supporting portion 53 and apair of spaced spring arms 55 extending therefrom. Near the end edge 61of the supporting portion 53, I have formed a slot 57 with an inwardlyand angularly turned tongue 59 extending toward end lwall 19. Forsecuring spring 51 on the bottom wall 11 of bese 5, slot 57 is firstslipped around boss 25 of the base. Then tab 23 of terminal 21 is pushedthrough base slot 13 from the inside of hollow portion 9. Tab 23 engagesthe outer transverse side 57a of slot 57 of spring 51 (as shown in FIG.4) and it Wedges the spring into a secure position when the terminal 21is sealed outside of base 5 (see also FIG. 2). The free end of tongue 59then frictionally engages wall 25C of boss V25 due to the wedging effectof terminal tab 23 upon spring 51, to restrain the spring supportingportion 53 from any longitudinal movement within base 5. Shoulders 27 ofterminal 21 bracket the side edges of spring 51 and engage wall 11 torestrain the spring support from any lateral slippage. End edge 61 ofspring 51 is also turned upwardly to engage the inner surface of sidewall 19 of the base and thus furnish further securement for the springwithin the switch housing.

With clutch spring 51 securely mounted in position on bottom wall 11 ofbase 5 (as shown in FIG. 2), resilient arms 55 each tangentially engagethe underside of pin 45 near its respective ends to bias the pin intofrictional engagement with bearing fingers 35 of terminal 21. A verysimplied slip-type clutching arrangement for rotatably supportingmovable contact 43 within base 5 has thus been achieved. Such aclutching arrangement, as shall hereinafter be described in detail,provides overtravel or slip-clutching action upon continuous tlexure ofthe bimetal in the same direction after movable contact 43 has alreadyengaged the hot or cold side contacts 44 and 46.

The hot and cold side contacts 44 and 46, respectively, represent thefixed contacts of my switch 1. As shown in FIG. 3, hot side contact 44is attached to L-shaped terminal 60 at contact supporting section 60ainside of base 5. Tab 601 of terminal 60 is extended through thelongitudinally extending slot 17 of base wall 11 and bent outwardly,being sealed to the outer surface of wall 11 by the aforementionedsealant, silicone rubber. Hot side contact 4dthus faces upwardly (asseen in FIG. 3) for engaging movable contact 43 upon down- -wardmovement thereof. Cold side contact 46 is attached to the elongated Lshaped terminal 62 at contact supporting section 62a. Tab 62h ofterminal 62 is extended through longitudinally extending slot 15 andbent outwardly, being sealed to the outer surface of wall 11 in the samemanner as terminal 60. Cold side contact 46 thus faces downwardly toengage movable contact 43 upon upward movement thereof. As shown onterminal 62 in FIGS. 3 and 4, side tab 62C has been angularly lancedfrom the flat surface of the intermediate area of cold contact terminal62 to help control the tolerances during assembly of the switch parts byengagement with an adjacent wall protrusion of the switch base 5.

Turning now to a very important aspect of my invention which provides animproved built-in self-starting feature for my llame detecting switch,it will be noted that underneath rotatable pin 415 on the side thereofdiametrically opposite to the side fastened to end 41 of the bimetal, Ihave welded one 4end of a J-shaped biasing or positioning rod 63. Asshown in FIG. l, elongated portion 64 of rod 63 extends longitudinallyunderneath the bimetallic arm 31 and is centrally ldisposed so that ithas freedom .to rotate with pin 45 between the spaced arms 55 of clutchspring 51 (see also FIG. 2). The other end of rod 63 is bentperpendicularly from the elongated portion 64 -to form connectingsection 65 `and then it is bent perpendicularly back in the generaldirection of but slightly away from pin 45 to form biasing supportsection 67. As shown in FIGS. 2 and 4, elongated portion 64 andconnecting section `65 are in a plane angularly related to bottom wall11. Section 67 is disposed at an `acute angle with respect to this plane(as shown in FIG. 2), and it is generally parallel to wall 11 when thetemperature is lless than F.

Pin 45 of my switch, with bimetallic arm 31 and biasing rod 63 attachedthereto, as shown in FIG. 4, provide a switch sub-assembly. When thissub-assembly is mounted in the assembly switch 1, as shall be furtherdescribed hereinafter, when the temperature of the switch is under 100F., biasing section 67 engages the inner surface of bottom wall 11 ofbase 5 to bias bimetallic arm 31 to its uppermost position (as shown inFIG. 2). Movyable contact 43 is Ithus normally biased into engagementwith cold side xed contact 46. The angular relationship between biasingsection 67 of rod 63 rand the plane described by portion 64 and section65 thereof, may be varied lto alter the upward biasing force exertedupon movable contact 43 during closure against cold contact 46, 'andthus adjust the predetermined temperature beneath which arm 31 will bebiased by rod 63.

Turning now to an explanation of the operation of my improved flamedetector switch 1, window 7 provides a transparent medium for the entryof radiant heat into hollow portion 9 of base 5. Bimetallic arm 31 willthus respond to the presence of a burner flame via radiation -and/ortemperature change. When the temperature is under 100 F. or any otherpredetermined selected temperature, rod 63 is in the position shown infull in FIG. 2. Biasing section 67 of rod 63 engages base wall 11 andserves as -a rigid support for rotatable bimetal arm 31 to normallymaintain movable contact 43 in engagement with cold side contact 46 (asshown in full in FIG. 2). In this manner, after switch 1 has been storedin a cold warehouse, or when it has been severely jarred or shakenduring shipment, biasing rod 63 will always assure that movable contact43 is in engagemen-t with the cold side fixed contact 46 when the flamedetector switch is placed 1n operation. As an example, if my amedetector switch is cooled to -40 F. and then brought back to roomtemperature, movable contact d3 will remain in continuous engagementwith the cold side fixed contact 46 until the ambient temperature hasreached 100 F.

When my switch 1 has been connected in a master furnace controllingcircuit for controlling a burner, it will then immediately start theburner because the cold side contacts are engaged. As the burner starts,the bimetal 31 will then flex downwardly to the dotted position 31hshown in FIG. 2. Movable Contact 43 will thus move from the cold side tothe hot side fixed contact, its position then being represented by thedotted contact 43a of FIG. 2. This action signals the condition of theflame to a prima-ry relay of the master control circuit in thewell-known manner. The burner will then, of course, gradually heat upthe bimetal. As the temperature increases, with the movable con-tact d3engaging the hot side con-tact 44, bimetal 31 tends to straighten itselfout and open the angle between its ends. More specifically, since thebimetal is fixed at the movable contact end by closure with the hot sidecontact 4d, bimetal 31 exes to position 31e of FIG. 2, and bent portion30 of bimetal 31 moves to position 30a. With an increase of temperatureof about 30 F., bimetal 31, will then turn rotatable pin i5 in acounterclockwise direction (as seen in FIG. 2) to slip the frictionalclutch provided by the engagement of pin 45 with the curved fingers 35.The biasing force provided by clutch spring 51 requires about a 30 F.rise in temperature to slip the clutch and rotate the pin 45. When thisclutch slippage occurs, Ibiasing rod 63 moves upwardly to the position63a (as shown in FIG. 2) to free supporting section 67 from the bottomwall 11 of the base. Rod 63 then no longer has any biasing effect uponbimetal 31.

In the event that the flame which is being `detected by my switch 1should fail, the bimetal contact 43 moves from the hot side `contacttoward the co-ld side contact. As soon as the movable contact 43 leavesthe hot side contact, this immediately shuts off the fuel supply. Thefrictional clutch is -arranged to prevent slippage of the pin d5 of therotatable bimetal until at least a 30 F. temperature drop is affectedand the movable contact 43 has moved from the hot side contact andtouches the cold side contact. Another 30 F. temperature `drop wipes themovable contact into the cold side contact, building up a torque equalto, and opposite to the clutch torque. With further cooling the clutchthen slips and the biasing rod 63 is thus returned to its originalbiasing position (with -supporting section 67 in engagement with bottomwall 11 of the case).

It will thus be seen that by means of my J-shaped biasing rod, I haveprovided a very efficient and simple means for maintaining the cold sidecontacts of my flame detector switch in continuous engagement when theambient temperature is under F.

In essence, I have thus pro-vided a fiame detector switch with animproved built-in self-starting arrangement. With this arrangement, myame detector switch in its preferred embodiment has a slip clutch whichoperates on temperature difference above 100 F. but operates as if the`bimetal were fastened to a rigid support at all temperature below 100F. It will be understood by those skilled in the art that thepredetermined temperature at which my flame detector biasing rod is tocease its biasing effect upon bimetallic arm 31 'may be varied inaccordance with the operational requirements for the particular switchapplication.

My improved ame detecting switch 1 has been designed principally formounting in the blast tube of a domestic gun-type oil burner. For thispurpose, I have illustrated it with one form of a mounting bracketassembly 69. This assembly (as shown in FIGS. 5 and 6) includes aU-shaped clip 71 which surrounds three sides of base 5 and partial-lybrackets the fourth side. Clamp 7 3 is welded to a flanged portion ofclip 71 and includes a threaded clamp screw 75 for attaching theassembly to a suitable support within the blast tube of a burner.Various other types of supporting bracket assemblies can, of cou-rse, beutilized for my improved flame `detector switch, in accordance with therequirements of the application.

It will thus be understood that my new and improved ame detecting switchsuch as herein illustrated provides a simple and efficient means fordetecting the presence of flame via radiation and/or temperature change,while also providing an improved means for assuring that the movablecontact of the switch will always start on the cold contact side of theswitch. It is thus no longer necessary to short out the terminals forstarting the furnace, because my improved tiame detecting switchincludes a simplified and expeditious means for biasing the movablecontact to the preferred starting position. It should be realized thatcertain aspects of my invention may be incorporated efficiently andbeneficially in other various types of thermally responsive switches.

While in accordance with the patent statutes, I have d-escribed what atpresent is considered to be the preferred embodiment of my invention, itwill be obvious to those skilled in the art that various changes andmodifications may be made therein without departing from my invention,and I, therefore, aim in the following claims to cover all suchequivalent variations as fall within the true spirit and scope of thisinvention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A thermally responsive device comprising an expansible andcontractable member, clutch means for rotatably supporting one end ofsaid member, movable contact means on the other end `of said member, apair of fixed contacts arranged to selectively cooperate with saidmovable `Contact means in response to the expansion and contraction ofsaid member thereby to control an electrical circuit, and a positioningmeans associated with the supported end of said member and acting uponsaid member to maintain said movable contact means in engagement with acer-tain one of said fixed contacts when the ambient temperature of saiddevice is less than a predetermined temperature value, thereby to assurethat said device may be started with its movable contact means inengagement with said certain fix-ed contact when said device isconnected in an electrical circuit and the ambient temperature of saiddevice is less than said predetermined value.

2. A thermally responsive switch comprising a thermally responsivemember, clutch means for rotatably supporting one end of said member, amovable contact positioned on the other end of said member, a pair ofspaced fixed contacts arranged on opposite sides of said movable contactand selectively cooperable therewith in 7' response to the thermallyresponsive movement of said member thereby to control an electricalcircuit, and a positioning means linked to the supported end of saidmember and acting thereupon to maintain Said movable contact inengagement with one of said iixed contacts when the ambient temperatureof said switch is less than a predetermined temperature value, therebyto assure that said switch may be started with its mo-vable contact inengagement with said one of said fixed contacts when the switch isconnected in an electrical circuit and the ambient temperature of saidswitch is less than said predetermined value.

3. A thermally responsive switch comprising a casing, said casingincluding a hollow cavity in which the mechanism of said switch ismounted and a transparent wall portion for admitting radiant heat intosaid cavity, a bimetallic contact arm positioned within said cavity,clutch means disposed Within said cavity for rotatably supporting oneend of said arm, a movable contact supported by the other end of saidarm, a pair of iixed contacts supported within said cavity and arrangedon opposite sides of said movable contact to selectively cooperatetherewith in response to the thermal expansion and contraction of saidbimetallic arm thereby to con-trol an electrical circuit, and apositioning means connected to the supported end of said arm and actingthereupon to mair1 tain said movable contact in engagement with one ofsaid fixed contacts when the ambient temperature of said switch is lessthan a predetermined temperature value, thereby to assure that saidswitch will be started with its movable contact in engagement with saidone of said fixed contacts when the switch is connected in an electricalcircuit and the ambient temperature of said switch is less than saidpredetermined value.

4. A thermally responsive ame detecting switch cornprising a casing,said casing including a hollow cavity in which the mechanism of saidswitch is mounted and a transparent wall portion for admitting radiantheat into said cavity, a bimetallic contact arm positioned within saidcavity, a cylindrical member tangentially aiiixed to one end of saidarm, a first terminal extending into said cavity, inner extension meanson said first terminal for receiving said cylindrical member, a springpositioned adjacent said iirst terminal within said cavity and urgingsaid cylindrical member into frictional engagement with said innerextension means thereby to provide a clutch means for controlling therotatable movement of said arm, a movable contact supported by the otherend of said arm, second and third terminals extending into said cavity,hot and cold side iixed contacts affixed to and supported by said secondand third terminals respectively, said ixed contacts arranged onopposite sides of said movable contact to selectively cooperatetherewith in response to the thermal expansion and contraction of saidbimetallic arm thereby to control an electrical apparatus, and apositioning rod attached to said cylindrical member and arranged to actupon said arm to maintain said movable contact in engagement with thecold side ixed contact when the ambient temperature of said switch isless than a predetermined temperature value, thereby to assure that saidiiame detecting switch will be started with its movable contact engagingthe cold side contact when the switch is connected in an electricalcircuit and 8 the ambient temperature of said switch is less than saidpredetermined value.

5. The switch defined in claim 4 wherein the positioning rod extendsbetween the cylindrical member to which it is attached and an inner wallof said casing to normally engage said casing.

6. The switch as defined in claim 4 wherein the bi* metallic Contact armcomprises an elongated strip of bimetallic material having side edgesconvergent toward the end of the arm which supports the movable contactand stepped inwardly near the end of the arm affixed to the cylindricalmember.

7. The switch as defined in claim 4 wherein the bimetallic contact armcomprises an elongated strip of bimetallic material having side edgesconvergent toward the end ot the arm which supports the movable contactand stepped inwardly adjacent the end of the arm affixed to thecylindrical member, said arm being bent angularly intermediate its ends.

8. The switch as dened in claim 4 wherein the spring which urges thecylindrical member into frictional engagement with the extension meansof the iirst terminal is of generally U-shaped configuration andincludes a spring biasing portion engaging said cylindrical member tocontinuously bias said member against said extension means, and asupported portion with a slot therein for receiving an inner boss of thecasing and thereby positioning said spring within the casing.

9. The switch as defined in claim 4 wherein said iirst, second and thirdterminals are supported by and extend inwardly through a wall of thecasing opposite to the transparent wall portion, and an inwardlyextending rectangular boss is formed in said wall adjacent said rstterminal, said spring having a generally U-shaped coniiguration and aslot therein for receiving said. boss, said first terminal extendingthrough said slot after said boss has been received by said slot therebyto wedge said spring into secure engagement with said wall.

l0. A thermally responsive switch comprising a bimetallic contact arm,clutch means for rotatably supporting one end of said arm, a movablecontact positioned on the other end of said arm, a pair of spaced ixedcontacts arranged on opposite sides of said movable contact andselectively cooperable therewith in response to the thermally responsivemovement of said bimetallic Varm thereby to control an electricalcircuit, iixed supporting means, and a positioning rod linked to thesupported end of said arm and arranged to engage said supporting meansto act upon said arm and maintain said movable contact in engagementwith one of said rixed contacts when the ambient temperature of saidswitch is less than a predetermined temperature value, thereby to assurethat said switch may be started with its movable contact in engagementwith said one of said iixed contacts when the switch is connected in anelectrical circuit and the ambient temperature of said switch is lessthan said predetermined value. l

References Cite-d in the tile of this patent UNITED STATES PATENTS2,503,259 Hall Apr. 11, 1950 2,660,645 Deubel Nov. 24, 1953 2,882,371Bishofberger Apr. 14, 1959 2,979,585 Werr Apr. il, 1961

